Turkish and American observers are hailing President Barack Obama's upcoming three-day visit to Turkey as an important step in repairing a significant - though troubled - strategic alliance.

Ankara and Washington had been at loggerheads on numerous occasions over the last few years. Turkey opposed the American invasion of Iraq and its parliament refused to pass a 2003 motion that would have allowed American troops to enter Iraq through Turkish soil. The United States, meanwhile, had at times been uncomfortable with Turkey's active re-engagement with the Middle East, particularly its growing relations with Syria and Iran.

During eight years of the Bush administration, Turkish public opinion of America reached new lows: a 2007 survey found that only 9 percent of Turks held a favorable view of the United States, down from 52 percent in 2002.

"I would say that we have had a very rough eight years - rough at the policy level, but also rough at the level of public opinion. And in modern times, public opinion has an impact on policy," says Ian Lesser, an expert on Turkey at the German Marshall Fund (GMF) of the United States in Washington.

Obama is scheduled to arrive in Turkey on April 5. While in the country, the US president is scheduled to meet with the country's leaders, address parliament and hold a town hall meeting with Turkish youth.

"I think Obama's visit can be quite transformative, depending on what he says to the Turkish parliament and what he says to Turkish society. People will be watching that very closely," Lesser said. "Because the relationship has not been one of trust for the last eight years, at least now there is a possibility to get to a much better climate for discussing substance."

There is certainly a lot of substance to talk about. The United States is looking to Turkey for help in its planned withdrawal from Iraq, and for its buildup of troops in Afghanistan. Ankara's improved relations with Syria and Iran, meanwhile, could be helpful for the Obama administration's plans to establish a dialogue with those two countries. Energy security and the development of new routes for delivering oil and gas to western markets are issues that could also benefit from Turkish-American cooperation, experts say.

Ilter Turan, a professor of international relations at Istanbul Bilgi University, says the problem of the last few years was not one of finding issues of mutual concern, but rather Turkish leaders felt ignored by Washington.

"The fact that you can identify common interests doesn't mean you are doing anything about it. Under the Bush administration, the mood was that the United States would devise the solutions and you might or might not agree with them, but you had to go along," Turan said.

"I think there are quite a significant number of common interests, and if we can reach an understanding that things will be managed by mutual consultation, and there will be moments when differences of opinion will prevail, then I think we can go into a period of healthy cooperation," Turan added.

Obama's coming to Turkey at the end of a European tour, rather than as part of a Middle East visit, also sends an important signal, Turan says. For many Turks, the Bush administration's efforts to portray Turkey as a "Muslim democracy" that could serve as a model for the rest of the Middle East and the wider Muslim world only worked to further widen the country's religious-secular divide.

"Turkey is now seen, not as a leading Muslim county in the Middle East, but again as a secular Muslim country that is an indivisible part of Europe. This makes it easier for Turkish policy elites to work with the United States and removes suspicion," he says.

Although the last eight years saw the Turkish-American relationship reach some very low points, observers warn against placing all the blame on missteps by the Bush administration. In many ways, the relationship - a pragmatic alliance born out of mutual needs and threats faced in the wake of the Cold War - has been struggling to find new meaning since the fall of the Soviet Union.

"Turkey and the United States are still working on redefining their relationship since the end of the Cold War. It's a work in progress," says Bulent Aliriza, director of the Turkey Project at the Center for Strategic and International Studies, a think tank based in Washington.

"It's a good thing that the president is coming so early in his term because it underlines Turkey's abiding importance" for American policy makers, he says. But, Aliriza cautioned; "there isn't yet a thought-through blueprint for the US-Turkish relationship."

One area where the two countries will need to clearly define their relationship is that of Turkey's emerging role in the Middle East, where Ankara has been trying to establish itself as a mediator and soft-power broker. In many ways, Ankara's more pronounced profile in the region has been the result of its filling a vacuum created by the Bush administration's disengagement from the Middle East and some of its thornier problems. But experts believe that Turkey and a United States that's more engaged in the region can work together.

"There is no question that Turkey can play a constructive role in the Middle East. It has gained the confidence of the regional players on most of the major issues of great importance. As a result, in an era of diminished resources for the United States, Turkey can be a critical ally in the pursuit of Washington and Ankara's overlapping interests," Steven Cook, a Washington-based senior fellow at the Council on Foreign Relations, wrote in recent briefing.

During a March visit to the United States, Ahmet Davutoglu, the Turkish prime minister's chief foreign policy advisor, predicted Obama's visit and the alignment of shared interests between Washington and Ankara could herald the arrival of a "golden age" in Turkish-American relations.

Although there are many positive signs, analysts warn that Obama's visit to Turkey is only the first step in a necessary process of rebuilding a frayed alliance. "A golden age would be terrific and who can argue with that as a goal," says GMF's Lesser. "But for those of us who watch this stuff, we'll be satisfied with a partnership where there is less mutual suspicion and a lot more cooperation on key issues."